1. Field of the Invention
The present invention relates to a fault protection system and method for a data communication environment, and more particularly to a fault protection system and method for a passive optical network.
2. Description of the Prior Art
Passive optical network (PON) architecture broadcasts downstream optical signals from optical line terminals (OLTs) to optical network units (ONUs) through optical channels composed of optical fibers and optical splitters. Due to passive elements based infrastructure which does not connect to any power consuming device, a passive optical network is advantaged by the low cost on both network construction and equipment maintenance. The advantages discussed above make the passive optical network a feasible and attractive technique in the field of optical network communication.
FIG. 1A shows a system structure diagram of a conventional passive optical network 100 including a host optical transmitting/receiving module (HOM) 110, a primary optical channel 120, and a plurality of client optical transmitting/receiving modules (COMs) 130-190. The host optical transmitting/receiving module 110 is an OLT broadcasting optical signals embedded with information through the primary optical channel 120. The client optical transmitting/receiving modules 130-190 are ONUs receiving the optical signals through optical splitters (not shown in FIG. 1) from the host optical transmitting/receiving module 110.
The conventional passive optical network 100 as shown in FIG. 1A lacks appropriate fault protection mechanism. When a broken line accidentally occurs somewhere in the primary optical channel 120, for example, some or all client optical transmitting/receiving modules will immediately fail to receive any information from the host optical transmitting/receiving module 110. FIG. 1B shows the passive optical network 100 of FIG. 1A with a broken line fault. If a broken line fault occurred at the “X” point as shown in FIG. 1B, while client optical transmitting/receiving modules 130, 140, and 150 are still capable of receiving host signals, client optical transmitting/receiving modules 160, 170, and 180 connected to the primary optical channel 120 after “X” point will be out of communication with the host optical transmitting/receiving module 110 at once.
FIG. 2 shows a system structure diagram of another conventional passive optical network 200 which contains a host optical transmitting/receiving module (HOM) 210, a primary optical channel 220, a secondary optical channel 222, a plurality of client optical transmitting/receiving modules (COMs) 230-280, and a plurality of optical splitter modules (OSMs) 232-282. In contrast with the structure diagram of FIG. 1A, the passive optical network 200 shown in FIG. 2 contains one more set of redundant equipments for each primary function. Besides the secondary optical channel 222, the host optical transmitting/receiving module 210 contains a primary host optical transmitting/receiving module (primary HOM) 210A and a secondary host optical transmitting/receiving module (secondary HOM) 210B. Each of client optical transmitting/receiving modules 230-280 also contains respective primary and secondary versions (primary COMs and secondary COMs). While the passive optical network 200 possesses a backup capability, it doubles the constructing cost on both client side and host side. Moreover, if any fault should happen simultaneously in both the primary optical channel 220 and the secondary optical channel 222, the structure shown in FIG. 2 is still incapable of keeping the normal communication of all client modules.
In view of the drawbacks of aforementioned conventional structure, there exists a need to provide a method and system to keep overall network communication at accidental faults without increasing cost for a passive optical network.